Dai-gonarthis Biographical information Race
Unknown Appears in
The Way of Kings (mentioned), Oathbringer (mentioned)
Dai-gonarthis is suspected to be one of the Unmade, a mysterious group of odious spren on Roshar.
"Let me no longer hurt! Let me no longer weep! Dai-gonarthis! The Black Fisher holds my sorrow and consumes it!"
–Tanatesach 1173, 28 seconds pre-death. A darkeyed female street juggler. Note similarity to sample 1172-89. 
If I'm correct and my research true, then the question remains. Who is the ninth Unmade? Is it truly Dai-Gonarthis? If so, could their actions have actually caused the complete destruction of Aimia?
–From Hessi's , page 307 Mythica 
Brandon has confirmed that the Unmade are Splinters of Odium. Odium splintered himself and created the Unmade to be his influence on Roshar. It is through the Unmade that Odium may be able to influence people in how they think or act.